SAC functions by inhibiting the activity of the anaphase-promoting complex/cyclosome (APC/C), a ubiquitin ligase that drives the cell cycle from metaphase to anaphase. When kinetochores are not properly attached, SAC proteins such as Mad2, BubR1, and Bub3 form a complex that inhibits APC/C. This halts the progression of the cell cycle, allowing time for the correction of attachment errors.
